SUPRAMOLECULAR SELF-ASSEMBY OF A NEW MULTI-CONFORMATIONAL SCHIFF BASE THROUGH HYDROGEN BONDS: CRYSTAL STRUCTURE, SPECTROSCOPIC AND THEORETICAL INVESTIGATION

ROCHA, MARIANA; DI SANTO, ALEJANDRO; ECHEVERRIA, GUSTAVO A; PIRO, OSCA E.; CUKIERNIK, FABIO D.; ULLIC, SONIA E.; GIL, DIEGO M.

JOURNAL OF MOLECULAR STRUCTURE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 1133 p. 24 - 26

0022-2860

The compound 4-(4-dimethylaminobenzylidene)aminoacetophenone was synthesized by condensation of 4-aminoacetophenone and 4-(dimethylamino) benzaldehyde in ethanol. This compound was characterized by CG-MS, infrared, Raman, UV-Vis, 1H and 13C NMR spectroscopy. The crystal structure was solved by single-crystal X-ray diffraction methods. The crystallographic data reveals that there are four independent molecules per asymmetric unit, that mainly differ from one another in rotations around the σ-bond of the azomethine N-atom with the phenyl ring. A detailed analysis of the intermolecular interactions in the four conformers of the compound has been performed using Hirshfeld surfaces and their associated two-dimensional fingerprint plots. The optimized geometrical parameters and calculated spectroscopic features obtained by quantum chemical calculations at B3LYP method show a very good agreement with the experimental data. Moreover, Natural Bond Orbital (NBO) analysis confirms the strong hyper-conjugative LP N(n1)→ σ* C(n9)-H interaction between the lone pair located in the N-atom of the azomethine group and the CH bond. Liquid crystalline properties of the Schiff base were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and Powder X-ray diffraction techniques. Mesomorphic behaviour was observed in this unsymmetrical azomethine. Based on POM and DSC measurements, the hexatic Smetic B phase was detected.